Magnetron keying circuit



June 12, 1956 T. L. GOTTIER MAGNETRON KEYING CIRCUIT Filed Nov. 14, 1952 POWER INVENTOR. THO/7H5 L. 6077758 MAGNETRON KEYING CIRCUIT Thomas L. Gottier, Los Angcles, Califi, assignor to the United States of America as represented by the Secretary of the Air Force Application November 14, 1952, Serial No. 320,509 9 Claims. (Cl. 250-36) This invention concerns a magnetron keying circuit for maintaining magnetron keyed transmissions of constant frequency.

In the past, magnetron keying has been accomplished by pulses imposed upon the magnetron accompanied by fluctuations in the potential balance from the addition of potential from the keying signals as power to the magnetron is turned on and off to the magnetron electrodes. These fluctuations cause alterations in the frequency at which pulses are emitted by the magnetron. In past magnetron practice no triggered circuit regulator has ever been i known to be applied successfully to a magnetron without effecting the magnetron frequency during keying operations.

An object of the present invention is to provide a voltage regulator magnetron keying circuit that during its operation permits the magnetron to maintain a predetermined frequency.

An illustrative embodiment of the present invention is shown in the accompanying schematic circuit drawing.

In the accompanying drawing, input energy from a coaxial cable 10 is passed through a potentiometer resistor 11 in series with a grid leak resistor 12 to the control grid of an amplifier tube 13. The control grid of the amplifier tube 13 is biased to ground through the grid leak resistor 12. A grid condenser 14 blocks the fiow of grid current and, with a potentiometer tap 15 adjustably contacting the potentiometer resistor 11 by-passes the grid resistor 12.

The amplifier tube 13 has its number two grid connected through a resistor 18 with its cathode. The cathode of the amplifier 13 is grounded through a resistor 19. The number three grid of the amplifier tube 13 is connected to its cathode. The plate-number two grid circuit of the amplifier tube 13 is connected across a potentiometer resistor 20 in series with another resistor 21. Plate current for the tube 13 is supplied from a source connected to the junction of the resistors 20 and 21. The potentiometer resistor 20 is shunted by a second potentiometer resistor 26.

A potentiometer tap 22 is adjustably applied to the potentiometer resistor 20 and is connected through a coupling capacitor 23 to the control grid of a second vacuum tube 30. The tube has its plate grounded through a resistor 31. The control grid of the tube 30 is connected through a grid resistor 32 and part of a potentiometer resistor 33 with the negative terminal of a power supply 35. The cathode of the tube 30 is connected through the other part of the potentiometer resistor 33 to the negative terminal of the power supply 35. The potentiometer resistor 33 is center connected to a movable potentiometer tap 34 adjustably engaging the potentiometer resistor 33. The number two grid of the tube 30 is connected through a resistor 41 with the positive electrode of a gas filled voltage regulator tube 40 that may be a neon glow tube or the like.

The tap 27 on the potentiometer winding 26 in the plate circuit of the tube 13 is connected through a capacitor 42 in series with a resistor 43 to the control grid Patented June 12, 1956 of a driving amplifier tube or a driver vacuum tube 45. The control grid of the driver vacuum tube 45 is connected through a resistor 46 to the negative terminal of the power supply 35 and through the series connected resistors 46, 47 and 48 with the positive terminal of the voltage regulator tube 40. The number two grid of the driver tube 45 is connected directly with the positive terminal of the voltage regulator tube 40. The plate and the number two grid of the driver tube 45 are connected together through series connected resistors 50 and 51, the junction of which is connected through another resistor 52 with the control grid of a grid controlled switching tube, a series regulator or magnetron current regulating tube 55. The cathode along with the heater of the driver tube 45 is keyed to or connected through a switch 44 with a power supply indicated by the transformer 49.

The positive terminal of the voltage regulator tube 40 is grounded through series connected resistors and 61, the junction of which is connected through another resistor 62 with the number two grid of the magnetron current regulator tube 55. The number two grid of the current regulator tube 55 is connected through a resistor with the negative terminal of the power supply 35 and through the series connected resistors 60 annd 62 with the positive electrode of the voltage regulator tube 40. The positive terminal of the power supply 35 is applied to ground. The cathode of the current regulating tube 55 is connected through a potentiometer resistor 63 with the negative terminal of the power supply 35. The potentiometer resistor 63 is adjustably engaged from one end of its potentiometer tap 64.

The plate of the current regulating tube 55 is connected directly to the cathode of the magnetron 70. The plate of the magnetron is connected to ground. Output from the magnetron 70 is taken from its loop 71 and is conducted by a wave guide 72 for radiation from its antenna 73.

Operatively, keying pulses efifective in keying on and off the magnetron 70 arrive from the coaxial line 10 and are impressed on the control grid of the amplifier tube 13. The output of the amplifier tube 13 appears in its plate cathode circuit across the parallel connected potentiometer resistors 20 and 26. Conduction of the tube 13 transmits an amplified keying pulse from the potentiometer tap 22 to the control grid of the power supply balancing vacuum tube 30 and from the potentiometer tap 27 to the control grid of the driver vacuum tube 45.

The tube 30 is connected in parallel across the power supply 35 such that when the tube 30 conducts on the arrival of an amplified keying pulse at its control grid its plate-cathode potential substantially matches that across the terminals of the power supply 35 and dampens any surge tendencies from the power supply 35 that might effect the frequency of the output from the magnetron 70 when keyed on and ofl.

The arrival of the amplified keying pulse across the resistor 46 at the control grid of the driver tube 45 causes this tube to conduct to the control grid of the series regulator tube or the magnetron current regulating tube 55.

The magnetron current regulator tube 55 is connected in series between the power supply 35 and the magnetron 70 with the regulator tube cathode connected with the negative terminal of the power supply 35 and the regulator tube plate connected with the cathode and the magnetron 70; Both the positive terminal of the power supply 35 and the plate of the magnetron '70 are applied to or are connected to ground.

The conduction of the magnetron current regulating tube 55, with the arrival of the keying pulse on its control grid from the plate of the driver tube 45, keys the magnetron 70 to transmit at a constant frequency. The

3 current regulating tube 55 provides a constant voltage to the cathode of the magnetron 70 while the magnetron is operating. The driver tube 45 'is cut off during the keying cycle, resulting in clean keying.

In the steady state condition, the driver tube 45 draws plate current through its plate resistor 51 and develops a voltage drop across the resistor 51. This drops the control grid to cathode voltage of the regulator tube 55 below plate current cut oif, allowing no current to flow from the plate of the regulator tube 55 to the cathode of a magnetron 70.

When a trigger pulse is applied to the control grid of the driver tube 45 from the amplifier tube 13, the driver tube 45 draws no plate current through its resistor 51, thereby allowing the grid voltage of the regulator tube 55 to rise above cut oil with respect to its cathode. Under this condition regulated voltage is applied by the regulator tube 55, acting as a current regulator, to the magnetron 70 maintaining its cathode at a constant current.

When the driver tube 45 is in a conductive condition the potential drop across the resistor 51 is sufiicient to bias the regulator tube 55 beyond its cut off point so that the magnetron 70 is inoperative.

Application of a negative keying pulse to the grid of the driver tube 45 reduces the tube voltage drop across the resistor 51 to zero and allows the regulator tube 55 to become conductive and to cause the magnetron 70 to conduct.

The anode-cathode circuit of the power supply balancing tube 30 maintains a constant load at all times on the power supply 35 since these circuits are connected in shunt. The load supplied by the tube 30 on the power supply 35 is substantially equal to that of the magnetron 70 when in operation. When the magnetron 70 is in operation the tube 30 is cut off by the keying pulse and imposes no load on the power supply 35. When the magnetron 70 is inoperative, the power supply balancing tube 30 conducts and impresses a load across the power supply 35 that is substantially the same as that applied while the magnetron 70 is in operation.

The disclosed circuitry has been submitted for the purposes of showing and explaining an operative embodiment of the present invention and similarly functioning modifications and substitutions of elements in the circuit may be made without departing from the scope of the invention.

What I claim is:

l. A circuit for pulse keying the output of a magnetron oscillator tube, comprising in combination a magnetron, a power supply, an operative first connection between said power supply and said magnetron including a grid controlled switching tube for conducting power to the magnetron during periods of time corresponding to the duration of keying pulses, a driving amplifier tube having as electrodes a plate, a cathode and a control grid, a

source of constant voltage for the plate circuit of said driver tube, a second operative connection between the control grid of said switching tube and the plate circuit of the driver tube such that the switching tube is rendered conducting when the driving tube is nonconducting, and means for applying negative keying pulses to the control grid of said driving amplifier tube to cause said driving amplifier tube to become nonconducting during the period of the keying pulses.

2. A circuit for pulse keying the output of a magnetron oscillator tube, comprising in combination, a magnetron having a cathode electrode, a power supply, an operative first connection between said power supply and said magnetron cathode electrode including a grid controlled switching tube for conducting power to the magnetron during periods of time corresponding to the duration of keying pulses, a driving amplifier tube having as electrodes a plate, a cathode and a control grid, a second operative connection between the plate electrode of said driver tube and the control grid of said switching tube, means for supplying a regulated constant potential to the plate electrode of said driving amplifier tube such that said switching tube is rendered conducting when the driving amplifier tube is nonconducting and means for applying negative potential pulses corresponding to the duration of the keying pulses to the control grid electrode of the driving amplifier tube to render the driving amplifier tube nonconducting for a period corresponding to the duration of each keying pulse and causing a positive constant potential to be applied to the grid of said switching tube for a time corresponding to the period said driving amplifier tube is rendered nonconducting.

3. A magnetron keying circuit for maintaining magnetron keyed transmissions at constant frequency, comprising the combination of a magnetron having an anode electrode applied to ground and an electron flow providing cathode electrode and a loop from which a constant frequency magnetron output is derived, a magnetron keying pulse source, a magnetron current regulating circuit inclusive of a vacuum tube having an anode electrode modifying variations in the magnetron cathode and having a control grid electrode deriving input keying pulses modified from the source thereof, pulse modulating circuit means between the magnetron keying pulse source and the magnetron current regulating tube, and a direct current power supply reference potential buffer ing changes in the output from the pulse modulating circuit means.

4. The circuit defined in the above claim 3 inclusive of a magnetron current regulating circuit voltage regulator tube as a part of the pulse modulating circuit means.

5. The circuit defined in the above claim 3 inclusive of a driver tube as a part of the pulse modulating circuit means and alternating its conduction function with that of the magnetron current regulating tube.

6. The circuit defined in the above claim 3 inclusive of a control grid actuated driver tube having a plate electrode passing its output to the magnetron current regulating tube control grid electrode in initiating conduction by the magnetron current regulating tube.

7. The circuit defined in the above claim 3 inclusive of a control grid actuated power supply balancing tube in the pulse modulating circuit means, and a control grid actuated driver tube in the magnetron current regulating circuit.

8. The circuit defined in the above claim 7 inclusive in the pulse modulating circuit means of a control grid actuated amplifier tube having a plate electrode and a number two grid electrode circuit shunted by two parallel connected potentiometer resistors separately adjustably contacted by movable taps separately coupled respectively with the control grid of the power supply balancing tube and the control grid of the driver tube.

9. A magnetron keying circuit for maintaining magnetron keyed transmissions at constant frequency, comprising a magnetron having a plate electrode applied to ground and having a cathode electrode and having a loop from which a constant frequency is available for transmission, a source of magnetron keying pulses, an amplifier circuit wherein an amplifier vacuum tube control grid electrode receives its input from the source of magnetron keying pulses and the amplifier vacuum tube having a number two grid electrode and a plate electrode from which amplifier tube output is derived by being shunted by two potentiometer resistors connected in parallel and separately variably contacted by first and second adjustable taps, a power supply balancing vacuum tube having a control grid electrode coupled with the first of the amplifier tube output conducting potentiometer taps, a driver vacuum tube having a control grid electrode coupled with the second of the amplifier tube output conducting potentiometer taps and the driver vacuum tube having an anode electrode, a direct current power supply with positive and negative terminals, a magnetron current regulating vacuum tube having as electrodes a plate electrode connected directly with and controlling the current level of the magnetron cathode electrode and having a control grid electrode receiving its input from the plate electrode of the driver vacuum tube, and a volt age regulating tube maintaining a positive potential on the control grid electrode of the magnetron current regulating vacuum tube.

References Cited in the file of this patent UNITED STATES PATENTS Shockley Mar. 4, 1947 Marke Dec. 27, 1949 Braden Feb. 6, 1951 Houghton Mar. 4, 1952 

